Ashley offers a very simple and easy to understand API. Here is an UML class diagram that will help you understand Ashley's architecture.

• Entity: simple containers of components.
• Component: interface for your game Components to implement, they are supposed to be bags of data with no logic whatsoever.
• ComponentMapper: provides super fast component retrieval of entities.
• Family: used to represent a set of entities with a specific collection of components.
• Engine: main class of the framework, manages all entities, systems and listeners.
• EntitySystem: allows you to implement game logic that may operate on entities of a given family.
• EntityListener: can be used to be notified of entity related events.